A lithium iron phosphate (LFP) battery is an environment-friendly battery. Compared with common lithium batteries, lithium iron phosphate batteries have the advantages of high safety, a long cycle life, fast charging and discharging, less weight at the same energy density, high temperature resistance, etc., and therefore have good application prospects. For example, lithium iron phosphate battery packs may be applied to EV (electric vehicles), ESS (Energy Storage Systems) and the like. The common applications include electric bicycles, electric buses and the like.
A lithium iron phosphate battery pack consists of a plurality of single cells connected in series. There are certain deviations among cells due to the limitations of the technological level, and cells will also have inconsistent capacity attenuation during use along with an increase in the number of charge-discharge cycles and due to the influence from storage time, temperature and the like, thus resulting in different states of charge (SoC) of cells in the same battery pack and the inequalization of cells in the same battery pack. SoC, also known as “remaining charge”, represents the ratio (expressed in percentage) of the remaining capacity of a battery after being used for a period of time or left unused for a long time to the capacity in its fully charged state. The value of SoC ranges from 0 to 1, wherein a battery is fully discharged when SoC=0 and fully charged when SoC=1.
Such inequalization of lithium iron phosphate battery packs will reduce the performance of lithium iron phosphate battery packs and shorten the service life of lithium iron phosphate battery packs. Accordingly, lithium iron phosphate battery packs require equalization such that a State of Charge (SoC) difference of each cell in a lithium iron phosphate battery pack is within a certain error range.